Aerogels are dried gels that are extremely light, with properties such as high porosities and large surface areas. Materials that are typically used for aerogels include silica, carbon, alumina or chalcogens. However, silica aerogels are extremely brittle and processes to form the above aerogels are costly, with some processes requiring solvents that are toxic to the environment.
Due to the low thermal conductivity of the aerogels, they have been investigated for use as thermal insulators. Greenhouse effect has been warming up the earth and threatening human life. It was found that CO2 emission from buildings contributed more than 30% of greenhouse gas emission in developed countries in 2005. Buildings also accounted for 39% of energy consumption in this year. Improving thermal insulation of buildings is one of the most effective solutions for the issue. Therefore, there have been many efforts in developing new insulation materials. Silica aerogels have been proposed as insulation materials for buildings. However, they are very brittle. A flexible aerogel-based insulation material (based on a composite containing methylsilylated Silica and polyethylene terephthalate) has been developed but it is much more expensive than conventional insulation materials.
High energy consumption, climate changes and the depletion of fossil fuels require more sustainable and energy efficient construction solutions. In order to meet the demand of improved energy efficiency, the thermal insulation of building plays an important role. To achieve better thermal insulation with current insulation materials, thicker walls are expected. However, this will increase the building cost and affect several issues like floor area, architectural restrictions, etc. As a result, it is essential to develop cheaper insulation materials with low thermal conductivity for construction applications. In tropical climates, high humidity is an additional factor affecting the lifetime of buildings. As the moisture content in the surrounding air is high, this may facilitate the growth of harmful microorganisms such as mould or bacteria that can cause allergy or respiratory problems. In addition, the high humidity of the air may cause condensation to form on surfaces that are exposed to the outside air such as windows, walls or ceilings, which can be colder than the outside air (due to the use of air-conditioners indoors). The condensed moisture potentially damages building materials.
While aerogels have limited applications in environmental cleanups such as cleaning chemical spills or removal of heavy metals from water, they have not been extensively investigated for use in other types of environmental contamination.
In order to clean up oil spills, sorbets have been used instead as an alternative to or together with traditional methods such as booms, skimmers, dispersants or burning. However, these traditional methods are not very effective to remove the oil completely from the water and are expensive. Sorbents for oil removal can be classified as inorganic mineral, synthetic organic and natural organic materials. The absorption capacities of common absorbents like polypropylene can be up to 25 times of their weight. However, the high cost and low biodegradability are the main drawbacks of this technique.
Aerogels also find limited use in applications that require the absorption of water. Due to the hygroscopic nature of aerogels such as silica aerogels, when the silica aerogels are placed in liquid water, the aerogel structure actually collapses due to the exertion of strong capillary forces by the absorbed water, leading to fracture of the solid silica backbone. Superabsorbent polymers are used instead to absorb water. Superabsorbent polymers are materials that have the ability to absorb and retain large volumes of water. As a result, they are used in water absorbing applications such as baby diapers and feminine napkins. They can swell in water to form rubbery gels that can be up to 99 wt % water. However, the absorbed water can only be removed by drying and the absorbents are not biodegradable.
There is a need to provide an aerogel that overcomes, or at least ameliorates, one or more of the disadvantages described above.